The role of the lung as an important metabolic organ is no longer in dispute. It participates actively in a variety of metabolic processes of great significance. Unlike most organs in the body, the lung comes in close contact with the environment and thus with the various pollutants therein. Chronic exposure to these pollutants, industrial toxicants, agriculture dust, adverse drug reaction and hypersensitivity involving altered immune mechanism may lead to adult respiratory distress syndrome. The lung pathology may appear in the form of pulmonary edema, lung fibrosis, emphysema or any other kind of pulmonary obstructive disease. The aim of the proposed investigation is to screen potentially desirable compound which could be of therapeutic value against lung fibrosis. In this regard, we have already succeeded in developing a consistently reliable model for producing lung fibrosis in hamsters by intratracheal administration of bleomycin. This model of lung fibrosis will be used to systematically evaluate and compare the effectiveness of several anticollagenous compounds such as Beta-amino propionitrile, para-aminobenzoic acid, 3, 4-dehydroproline, cis-4-hydroxy-L-proline, D-pencillamine and cytidine disphosphocholine in preventing and/or reversing the lung fibrosis following their administration by subcutaneous, intraperitoneal or inhalation (aerosols) route of administration. The ability of each compound in preventing and/or reversing the lung fibrotic changes will be evaluated by histopathologic quatitative morphometry and collagen biochemistry investigations of the lung. We believe that this type of multidisciplinary approach will not only provide a better understanding for the pathophysiological mechanism responsible for the genesis of lung fibrosis, but will also help us to search for a better therapeutically efficaceous anti-fibrotic compound.